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Old April 18th 09, 08:34 PM posted to rec.radio.amateur.antenna
Cecil Moore[_2_] Cecil Moore[_2_] is offline
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First recorded activity by RadioBanter: Mar 2007
Posts: 3,521
Default At resonant dipole with reactive characteristics.

Calltrex wrote:

"Cecil Moore" wrote the message
There is *no reactance* in an ideal resonant dipole!


I agree that the antenna is a chain of different pure resistances. But that
doesn't explain the asymmetric 'snapshot' here.


My grandsons must have interrupted and distracted me on
that earlier posting. I should have said there is no
extra reactance associated with different signs on
the voltage and current than there is when they have
the same sign. Any reactance on the left side has its
mirror image on the right side.

At the left side we see '+' voltage and '+' current and
at the right side we see '-' voltage and '+' current ! Why should it be
asymmetric?


It is asymmetric because the voltage envelope and current
envelope are spatially displaced by 90 degrees. If you
plot the voltage and current envelopes for 3 wavelengths
you will get the following - pardon the ASCII. One is the
sinusoidal voltage envelope and the other is the sinusoidal
current envelope.

/ \ / \ / \ /
/ \ / \ / \ /
------------------------------------------------------
\ / \ / \ /
\ / \ / \ /

/ \ / \ / \ /
/ \ / \ / \ /
------------------------------------------------------
/ \ / \ / \ /
\ / \ / \ /

Sometimes voltage and current have the same signs and sometimes
they have opposite signs. Remember, this is a snapshot in
time. 1/2 cycle later the envelopes will be upside down.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com